A hot corona above an accretion disc has electron temperature ( ) and Thomson optical…

PHYSICS · Multi-part · Fermi University Physics · Astrophysics & Cosmology · Radiation, radiative transfer and stellar atmospheres · Radiation, radiative transfer and stellar atmospheres

Stars from the Inside, Ch Hot and fast electrons: bremsstrahlung, Compton scattering and synchrotron emission

Problem

A hot corona above an accretion disc has electron temperature

k_BT_e = 50\,\mathrm{keV}

(

m_ec^2 = 511\,\mathrm{keV}

) and Thomson optical depth

\tau_{\rm es} = 2

. ((a)) Compute the fractional photon energy gain per scattering,

4k_BT_e/m_ec^2

. ((b)) Compute the mean number of scatterings a photon undergoes,

\max(\tau_{\rm es}, \tau_{\rm es}^2)

. ((c)) Form the Compton

y

parameter and decide whether soft photons passing through this corona are significantly reshaped into a hard power law.

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